ABA2-type triblock copolymer composed of PCL and PSt: synthesis and characterization

ABA(2)-type (Y-shaped) triblock copolymer made from poly(epsilon-caprolactone) (PCL) and polystyrene were synthesized by the combination of enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). First, CCl3-terminated PCL were synthesized by eROP of epsilon-caprolactone in the presence of initiator 2,2,2-trichloroethanol and biocatalyst Novozyme 435, followed by the esterification of the resulting PCL with 2,2-dichloro acetyl chloride to obtain trifunctional macroinitiator. The well-defined Y-shaped block copolymer was then synthesized by ATRP of styrene. The systems display characteristics of a living radical polymerization as indicated by linear first-order kinetics, linearly increasing molecular weight with conversion, and low polydispersities. The macromolecular structures and composition were characterized by HNMR, GPC, and FTIR. The thermal properties were characterized by differential scanning calorimetry.